https://segmentfault.com/a/

go的包不允许循环包含，具体例子：

main.go:

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package main
import (
    "fmt"
    "test/pkg1"
)
func main() {
    fmt.Println("in main.main")
    fmt.Printf("pkg1.Black=%s\n", pkg1.Black)
    fmt.Printf("pkg2.Black=%s\n", pkg2.Black)
}
func init() {
    fmt.Println("in main.init")
    fmt.Printf("pkg1.Black=%s\n", pkg1.Black)
    fmt.Printf("pkg2.Black=%s\n", pkg2.Black)
}

pkg1.go:

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package pkg1
import (
    "fmt"
    "test/pkg2"
)
const (
    Black string = "#000"
    white string = "#fff"
)
func init() {
    fmt.Println("in pkg1.init")
    fmt.Printf("pkg2.Black=%s\n", pkg2.Black)
}

pkg2.go:

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package pkg2
import (
    "fmt"
    "test/pkg1"
)
const (
    Black string = "#000"
    white string = "#fff"
)
func init() {
    fmt.Println("in pkg2.init")
    fmt.Printf("pkg1.Black=%s\n", pkg1.Black)
}

go build报错:

1
import cycle not allowed